1. Field of the Invention
This invention relates to a hydropneumatic automotive suspension system which has a hydraulic cylinder-piston device connected between a vehicle body and a wheel, and a gas spring which exerts a spring force according to the hydraulic pressure in the hydraulic chamber of the cylinder-piston device.
2. Description of the Prior Art
Though the automotive suspension system generally comprises a combination of a mechanical spring and a shock absorber, there also has been known a hydropneumatic suspension system, as disclosed in U.S. Pat. No. 4,162,091, which has a hydraulic cylinder-piston device connected between a vehicle body and a wheel, and a gas spring which exerts a spring force according to the hydraulic pressure in the hydraulic chamber of the cylinder-piston device.
The gas spring comprises a fluid chamber and a gas chamber which are defined in a casing and are separated from each other by a movable partition wall, and the fluid chamber is communicated with the hydraulic chamber of the hydraulic cylinder-piston device. The gas spring must be arranged so that when the hydraulic pressure in the hydraulic chamber changes due to bump or rebound of the wheel, the movable partition wall can be displaced or deformed to a position where the gas spring can exert a spring force according to the hydraulic pressure in the hydraulic chamber. For this purpose, the volume of the casing must be large. However, when the volume of the casing is large, the overall size of the gas spring is increased. Since it is very difficult to allot to the gas spring an integrated large space in the vicinity of the hydraulic cylinder-piston device, the gas spring has been obliged to be complicated in shape, which limits freedom in layout of the suspension system and adds to the manufacturing cost of the gas spring.